Grafted membranes and substrates having surfaces with switchable superoleophilicity and superoleophobicity and applications thereof

ABSTRACT

Disclosed herein are surface-modified membranes and other surface-modified substrates exhibiting switchable oleophobicity and oleophilicity in aqueous media. These membranes and substrates may be used for variety of applications, including controllable oil/water separation processes, oil spill cleanup, and oil/water purification. Also provided are the making and processing of such surface-modified membranes and other surface-modified substrates.

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/540,361, filed Sep. 28, 2011, which application isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to making and processing ofmembranes, and other materials and substrates with modified surfacesand/or switchable oleophilicity and oleophobicity in aqueous media. Alsoprovided is the making and processing of such surface-modified membranesand other surface-modified substrates.

2. Description of Related Art

Over millions of years of evolution, many marine animals such as fishhave developed skins capable of protecting them from marine fouling,which are accomplished by combining micro- and nanoscaled hierarchicalstructures and suitable surface chemistry. Meanwhile it has been alsorevealed that fish can survive in oil-polluted water owing to theiroleophobic scales. Oil wettability is of great importance for materialsused in aqueous or non-aqueous media, because of its application infields such as droplet manipulation in microfluidics, fabrication ofantifouling filtration membranes, and oil/water separation. In such way,an oil-water-solid system instead of the air-water-solid system becomesthe main concern.

Therefore, the design and preparation of surfaces with controllable oilwettability is highly desirable, particularly those that exhibitswitchable oleophobicity in aqueous media.

SUMMARY OF THE INVENTION

In one aspect of the present disclosure, there are providedsurface-modified materials comprising a substrate covalently bonded to apolymer, wherein the surface of the surface-modified material isoleophilic and/or hydrophobic under (or at or upon) a first conditionand oleophobic and/or hydrophilic under (or at or upon) a secondcondition, and wherein the polymer comprises a wettability-responsivepolymer, polymer segment or polymer block comprisingpoly(N-isopropylacrylamide), polyacrylamide, polypyrrole, polythiophene,polyaniline, poly(2-vinylpyridine), poly(4-vinylpyridine), poly(acrylicacid), poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride].

In some embodiments, the surface-modified material is oleophilic inaqueous media under a given condition. In some embodiments, thesurface-modified material is oleophobic in aqueous media under a secondcondition. In some embodiments, the surface-modified material isoleophilic in air under a first condition and oleophobic in air under asecond condition.

In some aspects, the switchable conditions involved in the switchingfrom oleophilicity to oleophobicity include temperature, voltage, pH,light illumination, pressure, or a combination thereof.

In some embodiments, the surface-modified material is oleophilic inaqueous media at a first temperature and oleophobic in aqueous media ata second temperature. In some embodiments, the surface-modified materialis oleophilic in air at a first temperature and oleophobic in air at asecond temperature.

In some embodiments, the surface-modified material is oleophilic inaqueous media at a first pH and oleophobic in aqueous media at a secondpH. In some embodiments, the surface-modified material is oleophilic inair at a first pH and oleophobic in air at a second pH. The pH values towhich the surface-modified material may be subjected is from the rangeof 1 to 14, in particular aspects.

In some embodiments, the surface-modified material is oleophilic inaqueous media exposed to a first voltage and oleophobic in aqueous mediaexposed to a second voltage. In some embodiments, the surface-modifiedmaterial is oleophilic in air exposed to a first voltage and oleophobicin air exposed to a second voltage. The values of voltage to which thesurface-modified material is exposed to may be from 0.1V to 5,000 V, incertain cases.

In some embodiments, the surface-modified material is oleophilic inaqueous media exposed to a first illuminance and oleophobic in aqueousmedia exposed to a second illuminance. In some embodiments, thesurface-modified material is oleophilic in air exposed to a firstilluminance and oleophobic in air exposed to a second illuminance. Thevalues of illuminance to which the surface-modified material is exposedto may be from 0.1 mW to 4.5 W with wavelength from 10 nm to 1,000 μm,in some embodiments.

In some embodiments, the surface-modified material is oleophilic inaqueous media under a first pressure and oleophobic in aqueous mediaunder a second pressure. In some embodiments, the surface-modifiedmaterial is oleophilic in air under a first pressure and oleophobic inair under a second pressure. The values of pressure to which thesurface-modified material is exposed may be from 0.1 Pa to 10⁶ Pa, inparticular embodiments. In some embodiments, the substrate comprises aplurality of imbedded nanostructures. In some embodiments, thenanostructures comprise nanoparticles, nanowires, nanorods, nanobelts,nanotubes, layered nanostructures, or a combination of these. In someembodiments, the nanostructures comprise silica, carbon, metal, metaloxide of the metal, hybrid of the metals, hybrid of the metal oxides, orpolymers. In some embodiments, the nanostructures comprise silica. Insome embodiments, the nanostructures have an average size from around 1nm to 10 μm in at least one dimension. In some embodiments, thesubstrate does not comprise a plurality of imbedded nanostructures.

In some embodiments, the polymer comprises a block copolymer or mixedpolymer. In some embodiments, the polymer comprises a block copolymercomprising two or three blocks. In some embodiments, the block copolymercomprises at least one wettability-responsive block. In someembodiments, the wettability-responsive block ispoly(N-isopropylacrylamide), polyacrylamide, polypyrrole, polythiophene,polyaniline, poly(2-vinylpyridine), poly(4-vinylpyridine), poly(acrylicacid), poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride].In some embodiments, the block copolymer comprises at least onehydrophobic block. In some embodiments, the hydrophobic block ispoly(acrylonitrile), poly(phenyl methyl siloxane), polystyrene,poly(4-dimethylsilyl styrene), poly(4-methyl styrene), poly(dimethylsiloxane), polyethylene, polypropylene, poly(isobutylene), polyamide,poly(vinylidene fluoride).

In some embodiments, the polymer comprises a mixed polymer comprising atleast one hydrophobic homogenous polymer and one polymer that isresponsive to wettability. In some embodiments, the hydrophobichomogenous polymer is poly(acrylonitrile), poly(phenyl methyl siloxane),polystyrene, poly(4-dimethylsilyl styrene), poly(4-methyl styrene),poly(dimethyl siloxane), polyethylene, polypropylene, poly(isobutylene),polyamide, or poly(vinylidene fluoride). In some embodiments, thewettability-responsive polymer is poly(N-isopropylacrylamide),polyacrylamide, polypyrrole, polythiophene, polyaniline,poly(2-vinylpyridine), poly(4-vinylpyridine), poly(acrylic acid),poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],or mixtures of thereof.

In some embodiments, the substrate comprises a textile, a membrane, apolymer foam, a metal mesh, a metal foam, paper, glass, ornanostructures. In some embodiments, the textile, membrane, paper, metalmesh, metal foam or polymer foam has an average pore size in the rangefrom 10 nm to 5,000 μm. In some embodiments, the substrate comprises anonporous solid. In some embodiments, the textile, membrane, or polymerfoam comprises cellulose, nylon, polyester, polyethylene terephthalate,polyurethane polylactide, polypropylene, polyethylene, polysulfone,polyamide, polyvinyl chloride, polytetrafluoroethylene, polycarbonate,polyacrylonitrile, polybutylene terephthalate, polyimide, polymethylmethacrylate, polyetheretherketone, polyetherketone, polyetherimide,polyethersulfone, polymethylpentene, polyoxymethylene, polyphthalamide,polyphenylene oxide, polyphenylene sulfide, ethylene propylene rubber,styrene butadiene rubber, ethylene propylene diene monomer rubber,chitosan, alginate, gelatin, poly(N-isopropylacrylamide),poly(4-vinylpyridine), poly(2-vinylpyridine), polydimethylsiloxane,poly(phenyl methyl siloxane), poly(4-dimethylsilyl styrene),poly(4-methyl styrene), poly(isobutylene), poly(N-isopropylacrylamide),polyacrylamide, polypyrrole, polythiophene, polyaniline, poly(acrylicacid), poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],polyvinylpyrrolidone, or mixtures or blends thereof. In someembodiments, the nanostructures as the substrate comprise nanoparticles,nanowires, nanorods, nanobelts, nanotubes, layered nanostructures, or acombination of these. In some embodiments, the nanostructures comprisesilica, carbon, metal, metal oxide of the metal, hybrid of the metals,hybrid of the metal oxides, or polymers. In some embodiments, thenanostructures have an average size from around 1 nm to 100 μm in atleast one dimension. In some embodiments, the nanostructures are porous.In some embodiments, the pore size of the porous nanostructures isbetween 0.3 nm to 200 nm. In some embodiments, the nanostructures arecore-shell structures. In some embodiments, the core-shell structurescomprise a magnetic core and a shell. In some embodiments, thecore-shell structures comprise a hollow core and a shell. In someembodiments, the shell of the core-shell structures is porous. In someembodiments, the pore size of the porous shell is between 0.1 nm to 200nm. In some embodiments, the shell of the core-shell structures isnon-porous. In some embodiments, the core of the core-shell structurescomprise silica, carbon, metal, metal oxide of the metal, hybrid of themetals, hybrid of the metal oxides, or polymers. In some embodiments,the shell of the core-shell structures comprise silica, carbon, metal,metal oxide of the metal, hybrid of the metals, hybrid of the metaloxides, or polymers.

In some embodiments, the metal mesh or metal foam comprises metal, metaloxide of the metal, metal chloride of the metal, metal hydroxide of themetal, alloy of the metals, hybrids of the metal oxides, hybrids of themetal chlorides, or hybrids of the metal hydroxides. In someembodiments, the metal comprises at least one of copper, iron, nickel,titanium, zinc, aluminum, silver, gold, palladium, platinum, silicon,vanadium, zirconium, cobalt, lead, chromium, barium, manganese,magnesium, yttrium, hafnium, thallium, indium, tin, arsenic, selenium,tellurium, bismuth, gallium, germanium, cadmium, iridium, tungsten,tantalum, niobium, molybdenum, strontium, calcium, an alloy thereof, anoxide thereof, or a mixture thereof.

In some embodiments, the nonporous solid comprises the same chemicalcompositions as the textile, filter membrane, or polymer foam. In someembodiments, the nonporous solid comprises the same chemicalcompositions as the metal mesh or metal foam.

In some embodiments, the polymer was bonded to the substrate through agrafting to and/or grafting from process. In some embodiments, thegrafting from process comprises atom transfer radical polymerization orreversible addition-fragmentation chain transfer polymerization. In someembodiments, the grafting to process comprises functionalized polymermolecules reacting with complementary functional groups located on thesubstrate surface to form tethered chains. In some embodiments, thefunctional groups of the functionalized polymer molecules comprise aminogroups, pyridyl groups, carboxy groups, and/or hydroxy groups. In someembodiments, the complementary functional groups located on thesubstrate surface comprise epoxy groups, amino groups, carboxy groups,hydroxy groups, haloalkyl groups. In some embodiments, the complementaryfunctional groups are introduced on the substrate surface by asilanization reaction between a silane and the substrate. In someembodiments, the silane comprises an epoxy group, amino group, carboxygroup, hydroxyl group, haloalkyl group.

In another aspect, there are provided surface-modified materialscomprising a substrate covalently bonded to a polymer, wherein thesubstrate comprises a plurality of silanized silica particles and thepolymer comprises a plurality of pyridyl groups.

In some embodiments, the substrate further comprises a textile, a metalmesh, paper, a metal foam or a polymer foam. In some embodiments, thesubstrate is a textile.

In some embodiments, the textile comprises cellulose. In someembodiments, the textile comprises polypropylene.

In some embodiments, the substrate comprises a polymer foam. In someembodiments, the polymer foam is a polyurethane.

In some embodiments, the silanized silica particles are further definedas silanized silica nanoparticles. In some embodiments, the silanizedsilica particles are silanized using (3-bromopropyl)trimethoxysilane. Insome embodiments, the polymer is a poly(2-vinylpyridine-b-dimethylsiloxane) block copolymer.

In another aspect, there are provided methods of separating oil fromwater, comprising:

-   -   a. obtaining a surface-modified material disclosed herein;    -   b. contacting the surface-modified material with a mixture        comprising oil and water; and    -   c. adjusting a condition (temperature, voltage, pH, light        illumination, pressure, or a combination thereof, for example)        of the mixture until more oil than water adheres to the        surface-modified material.

In another aspect, there are provided surface-modified materialscomprising a substrate covalently bonded to a polymer, wherein thepolymer comprises a plurality of nitrogen-containingheteroaryl_((C3-12)) groups, and wherein the surface of thesurface-modified material is oleophilic under a first condition andoleophobic under a second condition. In some embodiments, thenitrogen-containing heteroaryl_((C3-12)) groups are further defined aspyridyl groups.

Other objects, features and advantages of the present disclosure willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating specific embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentdisclosure. The invention may be better understood by reference to oneof these drawings in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1 depicts a scheme for the surface modification of textile fabrics.

FIGS. 2 a-d depict SEM images of the textile fabrics: (FIG. 2 a) and(FIG. 2 b), raw textile fibers; (FIG. 2 c) and (FIG. 2 d), after thesilica nanoparticles deposition and block copolymer grafting.

FIGS. 3 a & b depict still images from video contact angle measurementsfor a neutral water droplet (FIG. 2 a) and oil droplet (FIG. 2 b)applied on the surface in air.

FIGS. 4 a-c. FIG. 4 a depicts still images from video contact anglemeasurements for an acidic droplet (pH=1.0) applied on the surface ofthe as-modified textile in air. FIG. 4 b provides contact angles as afunction of pH values of the applied water droplets on block copolymergrafted textile. All the contact angles were calculated after a stableshape of droplet was reached on these surfaces. FIG. 4 c showstime-dependent changes in contact angle for water droplets withdifferent pH values: square, pH 1.0; triangle, 2.0; circle, pH 6.5. Theinset in c) shows the details of time-dependent changes in contact anglefor water of pH 1.0.

FIGS. 5 a-f. FIG. 5 a depicts still images from video contact anglemeasurements for DCE droplet applied on the surface of the as-modifiedtextile under water of pH 6.5. FIG. 5 b shows photographs of DCEdroplets upon contacting the block copolymer grafted textile under waterof pH 6.5. FIG. 5 c provides a schematic representation of oilwettability of the prepared surface in water of pH 6.5. FIG. 5 d showsimage of DCE droplet applied on the surface of the block copolymergrafted textile in water of pH 2.0. FIG. 5 e shows a photograph of DCEdroplets sitting on the block copolymer grafted textile under acidicwater of pH 2.0. The DEC droplets were stained with oil red for clearobservation. FIG. 5 f provides a schematic representation of the oilwettability of the prepared surface in water of pH 2.0.

FIG. 6—Reversible surface wettability of the copolymer grafted textiles.Squares: contact angles of water droplets at pH 6.5 (even cycles) and pH2.0 (odd cycles) in air; circles: contact angles of DCE droplets on thesurface in water of pH 6.5 (even cycles) and pH 2.0 (odd cycles).

FIGS. 7 a & b—Setups for controllable water/oil separation. FIG. 7 ashows the modified textile was fixed between two glass tubes as aseparation membrane, the mixture of gasoline and water was poured intothe upper glass tube. Gasoline selectively passed through the textile,while water was repelled and held in the upper glass tube (right panel).FIG. 7 b shows acidic water wetted textile for the water/oil separationprocess. Water selectively passed through the textile, while gasolinewas repelled and held in the upper glass tube.

FIGS. 8 a-c are photographs of the oil capture and release process.FIGS. 8 a & b show oil absorption by the functionalized foam in neutralwater. FIG. 8 c shows the release of the absorbed oil in acidic water.

FIGS. 9 a-d are examples showing the responsive core-shellnanostructures for the manipulation of small volumes of water. FIG. 9 ashows the preparation scheme and TEM images of the responsive core-shellnanoparticles. FIG. 9 b shows the pH-responsive property of theresponsive nanoparticles. FIG. 9 c shows the preparation of the liquidmarbles with the responsive nanostructures and the controllablemanipulation of the liquid marbles. FIG. 9 d shows the UV triggeredrupture of the liquid marble prepared using the PAG loadedfunctionalized nanoparticles.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In some aspects of the present invention, there are provided materials,substrates and membranes comprising surfaces with switchableoleophilicity and oleophobicity in aqueous media in response totemperature, voltage, pH, light illumination, pressure, or a combinationthereof. In some embodiments, this switch may be tied to pH, resultingin pH switchable oil wettability. As discussed in greater detail below,some of these surface-modified materials are oleophilic at neutral pHand oleophobic at acidic pH. These surfaces of membranes and substratesmay be used in a variety of applications, including controllableoil/water separation processes, oil spill cleanup, oil/waterpurification, self-cleaning surfaces, microfluidics, liquid dropletmanipulation, etc. Preparation of Surface-Modified Materials

In one aspect of the present disclosure, there are providedsurface-modified membranes and substrates by grafting or depositing onthe surface different materials such as polymers or copolymers on theirentirety or in combination with nanoparticles. The grafting processesdisclosed herein and modifications thereof may be used to render asurface oleophilic or, in some embodiments, provide a surface withswitchable and/or tunable oleophilicity. Hence, in some parts of thisdisclosure a mechanism and a method has been described whereby surfaceoleophilic properties can be interchangeable or switchable.

In some aspects of the present disclosure there are providedsurface-modified membranes or other materials exhibiting switchableoleophilic/oleophobic properties. In some embodiments, these materialsmay be coated using a responsive block copolymer grafting strategy. Forexample, a layer of organo-silicon based molecules may be deposited onor bound to the surface of membrane or substrate, e.g., a textile or apolyurethane foam, to produce a surface with a hierarchical structure,which can amplify the wetting property of the surface. In someembodiments, a block copolymer comprising poly(2-vinyl pyridine) andpolydimethylsiloxane segments (i.e., P2VP-b-PDMS) is then grafted ontothe deposited silica nanoparticles. In some embodiments, the resultingsurfaces of the modified membranes or other materials are hydrophobic atneutral pH and hydrophilic at acidic pH. Without being bound by theory,in the case of a poly(2-vinyl pyridine) copolymer, these propertiesresult from the protonation/deprotonation of nitrogen-containingheteroaryl groups, e.g., pyridine groups, as a function of pH.

Generally, to achieve an extreme wetting behavior, a rough surface withhierarchically micro- and nanostructures is a prerequisite, as thewetting property can be amplified by the surface roughness at differentlength scales. Suitable substrates for these surface-modified membranesand other materials include textiles (fabrics), metal mesh, filterpaper, metal, polymeric foams (e.g., polyurethane foams), glass andwood.

Textile fabric may desirable in some embodiments because of its lowcost, wide availability, chemical and mechanical robustness, andinherent fiber-textured structures which provide micro-structuredroughness. The procedure for the preparation of the surface on thetextile fabric with switchable oleophilicity and oleophobicity inaqueous medium is schematically illustrated in FIG. 1. Additionaldetails related to a specific embodiment are provided in Example 2below.

A three-dimensional porous polyurethane foam used for packaging can bealso employed as a substrate for a P2VP-b-PDMS grafting procedure.Polyurethanes are reaction polymers. A urethane linkage is produced byreacting an isocyanate group, —N═C═O with a hydroxy group, andpolyurethanes are produced by the polyaddition reaction of apolyisocyanate with a diol or a polyol, typically in the presence of acatalyst and other additives. A polyisocyanate is a molecule with two ormore isocyanate functional groups, R—(N═C═O)_(n), wherein n≦2 and apolyol is a molecule with two or more hydroxyl functional groups,R′−(OH)_(n), wherein ≧2. The reaction product is a polymer containingthe urethane linkage, —RNHCOOR′—. Polyurethanes may be produced byreacting a liquid isocyanate with a liquid blend of polyols, catalyst,and other additives. The blend of polyols and other additives may alsobe called a resin or a resin blend. In some embodiments, resin blendadditives may include chain extenders, cross linkers, surfactants, flameretardants, blowing agents, pigments, and/or fillers. The choice ofinitiator, extender, and molecular weight of the polyol will typicallyaffect its physical state, and the physical properties of the resultingpolyurethane. Important characteristics of polyols are their molecularbackbone, initiator, molecular weight, % primary hydroxyl groups,functionality, and viscosity.

In some embodiments, the polyurethane-based surface-modified membranesand other materials provided herein exhibit oleophilicity in neutralaqueous medium, and can be easily switched into oleophobic when wettedby acidic water. For example, a foam functionalized in this manner maybe used for the oil-spill cleanup applications (FIGS. 8 a & b andExample 5).

In some embodiments, surface-modified membranes or other materials havebeen impregnated with nanoparticles. In other embodiments, they have notbeen impregnated with nanoparticles. In some embodiments, thenanoparticles are silica. In other embodiments, nanoparticles other thansilica are also contemplated. For example, such other nanoparticlesinclude carbon nanotubes, nanoclays, zeolites, iron oxides, silvernanoparticles, copper oxides, titanium dioxide, carbon black, etc.

These methods can be further modified and optimized using the principlesand techniques of chemistry and materials science as applied by a personskilled in the art.

Properties of Surface-Modified Membranes and Substrates

The surface-modified membranes and other materials provided hereinexhibit a range of useful properties, and they may be used in a varietyof applications, including oil spill cleanup, oil/water purification,etc. For example, surface-modified membranes and other materials thatexhibit pH switchable wettability may be used to control underwater oilwettability of membranes other substrates and apparatuses. In some ofthe embodiments, the surface-modified membranes and other materials areoleophilic at neutral pH and oleophobic at acidic pH. As an example ofan application, such a material, including a block polymer graftedtextile fabric, may be used to provide controllable oil/water separationprocesses.

Wettability of a surface is typically governed by the surface chemistryas well as the surface roughness. In some embodiments, wettability isevaluated by contact angle measurements. The results discussed in theExample section confirm that P2VP-b-PDMS grafted textile exhibitstunable wetting behavior to water, depending on water pH, switchingbetween hydrophobicity and hydrophilicity. The switchable waterwettability of the surface is expected to affect its oil wettability inaqueous media. FIG. 5 presents the oil wettability of the P2VP-b-PDMSgrafted textile under water of different pH values, with DCErepresenting an oil phase. On contact, the textile immediately sucked upthe DCE droplets without leaving behind any residues. This simpleexperiment revealed that the block copolymer grafted membranes andsubstrates are promising sorbents for removing oil from water.

In some embodiments, the surface-modified membranes and othersurface-modified materials provided herein are hydrophobic to water atpH≧3, which means the surface is nonwettable in these aqueous media. Asa result, when the surface-modified material is immersed in neutralwater, the surface is still covered with the oleophilic PDMS chains, andtherefore once an oil droplet contacts the surface, oil wets the surfacepreferentially over water, owing to the oleophilic surface property(FIG. 5 c).

In some embodiments, air can be trapped inside the rough grooves ofsurface-modified membranes and substrates when submerged in water. Theas-prepared block copolymer grafted textile surface is hydrophobic inair. A complex interfacial system, i.e., a four phase system(air-solid-oil-water), will then be formed when an oil droplet contactssuch a surface.

In some embodiments, when the surface-modified membranes and substratesprovided herein are immersed in acidic water, for example pH of 2.0, theoil wettability of the surface reversed completely. As has beendiscussed in greater detail below, the present invention providessurface-modified membranes and substrates that are hydrophilic in acidicwater. Under such conditions, water can readily wet the surface anddiffuse into micro- and nanostructures of the textile, forming a watertrapped composite interface.

In some embodiments, e.g., after being rinsed with neutral water anddried, the acid-wetted surface can easily recover its hydrophobic andoleophilic properties in neutral aqueous medium, consistent withswitchable oleophobicity and oleophilicity in aqueous media. In someembodiments, the surface properties may be switched reversibly withoutany significant change in the pH-responsive property of the surface(FIG. 6).

From the results presented in the examples section below, some of thesurface-modified membranes and substrates provided herein, includingP2VP-b-PDMS grafted textiles, exhibit switchable oleophobicity andoleophilicity in aqueous medium with different pH values. Suchsurface-modified membranes and substrates are expected to be very usefulto membranes and substrates for underwater applications. For example, insome embodiments, it was shown that such surface-modified membranes andsubstrates can be used for the controllable water/oil separation (FIG.7). The ease with which the permeability of the block copolymer graftedtextile toward oil and water is selectively switched means the samepiece of material can be used for different separation purposes.

Oil Spill Cleanup

In some embodiments, the membranes and substrates and methods disclosedherein may be used for the clean-up and/or remediation of oil orhydrocarbon spills and pollution.

An oil spill is the release of a liquid petroleum hydrocarbon into theenvironment, typically due to human activity. Often the term refers tomarine oil spills, where oil is released into the ocean or coastalwaters. The oil may be a variety of materials, including crude oil,refined petroleum products, such as gasoline or diesel fuel, oily refuseor oil mixed in waste, or hydrocarbons generally. Oil may also enter themarine environment from natural oil seeps.

The environmental effects include damage to wildlife, water purity andcoastal areas. For example, oil will coat the feathers of birds, therebyreducing their insulating ability and make the birds more vulnerable totemperature fluctuations and much less buoyant in the water. Oil alsoimpairs bird flight abilities. As they attempt to preen, birds typicallyingest oil that covers their feathers, causing kidney damage, alteredliver function, and digestive tract irritation. This and the limitedforaging ability quickly causes dehydration and metabolic imbalances.Many birds affected by an oil spill will die unless there is humanintervention.

Other marine mammals are affected as well. For example, oil will coatthe fur of sea otters and seals, reducing their insulation abilities andleading to body temperature fluctuations and hypothermia. Ingestion ofthe oil causes dehydration and impaired digestions. Beyond mammals, fishand invertebrates are also typically affected.

Plant and algae species may also be affected by an oil spill. Forexample, because oil floats on top of water, less sunlight penetratesinto the water, limiting the photosynthesis of marine plants andphytoplankton.

By decreasing and disabling flora and fauna populations, part or all ofa given coastal and/or marine ecosystem may be affected by an oil spill.

Recovering oil depends upon many factors, including the type of oilspilled, the temperature of the water (in warmer waters, some oil mayevaporate), and the types of shorelines and beaches involved.

Both crude oil and natural gas are predominantly a complex mixture ofhydrocarbons of various molecular weights, and other organic compounds,that are found in geologic formations beneath the Earth's surface. Undersurface pressure and temperature conditions, the lighter hydrocarbonsmethane, ethane, propane and butane occur as gases, while the heavierones from pentane and up are in the form of liquids or solids. However,in the underground oil reservoir the proportion which is gas or liquidvaries depending on the subsurface conditions, and on the phase diagramof the petroleum mixture.

The majority of hydrocarbons found naturally occur in crude oil, wheredecomposed organic matter provides an abundance of carbon and hydrogenwhich, when bonded, can catenate to form seemingly limitless chains.Extracted hydrocarbons in a liquid form are referred to as petroleum ormineral oil. A hydrocarbon is an organic compound consisting entirely ofhydrogen and carbon. Aromatic hydrocarbons (arenes), alkanes, alkenes,cycloalkanes and alkyne-based compounds are different types ofhydrocarbons. The hydrocarbons in crude oil are mostly alkanes,cycloalkanes and various aromatic hydrocarbons while the other organiccompounds contain nitrogen, oxygen and sulfur, and trace amounts ofmetals such as iron, nickel, copper and vanadium. The exact molecularcomposition varies widely from formation to formation.

Hydrocarbons are one of the Earth's most important energy resources. Thepredominant use of hydrocarbons is as a combustible fuel source. Intheir solid form, hydrocarbons take the form of asphalt. The C₆ throughC₁₀ alkanes, alkenes and isomeric cycloalkanes are the top components ofgasoline, naptha, jet fuel and specialized industrial solvent mixtures.With the progressive addition of carbon units, the simple non-ringstructured hydrocarbons have higher viscosities, lubricating indices,boiling points, solidification temperatures, and deeper color.

The proportion of light hydrocarbons in the petroleum mixture istypically highly variable between different oil fields and ranges fromas much as 97% by weight in the lighter oils to as little as 50% in theheavier oils and bitumens.

In one aspect, the invention provides membranes and substrates that maybe used to reduce hydrocarbon pollution to an acceptable level. In someembodiments, the method removes greater than 90%, 95% or 98% of thehydrocarbon from the contaminated site, for example, from water orshoreline.

The methods, membranes and substrates and compositions provided hereinmay be combined with other cleanup methods, including bioremediation,use of accelerators, controlled burning, use of dispersants ordetergents, skimming, use of booms, or use of vacuums.

Bioremediation involves the use of microorganisms or biological agentsto break down or remove oil.

Accelerators are hydrophobic chemicals, containing no bacteria, whichchemically and physically bond to both soluble and insolublehydrocarbons. The accelerator acts as a herding agent in water and onthe surface, floating molecules to the surface of the water to formgel-like agglomerations.

Controlled burning can effectively reduce the amount of oil in water.

Dispersants and detergents will typically clustering around oil globulesand allowing them to be carried away in the water.

Dredging may be used for oils dispersed with detergents and other oilsdenser than water.

Skimming may be used in combination the methods and compositionsdisclosed herein. Typically, this requires relatively calm waters.

The present methods and compositions may be combined with booms, whichare large floating barriers that round up oil and may lift the oil offthe water

Vacuums may be used to remove oil from beaches and water surface.Similarly, shovels and other road equipments may be used to clean up oilon beaches.

DEFINITIONS

The use of the word “a” or “an,” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.”

Throughout this application, the term “about” is used to indicate that avalue includes the inherent variation of error for the device, themethod being employed to determine the value, or the variation thatexists among the study subjects.

The term “adsorb” is taken to include both “adsorb” and “absorb” as wellas both processes combined.

The terms “comprise,” “have” and “include” are open-ended linking verbs.Any forms or tenses of one or more of these verbs, such as “comprises,”“comprising,” “has,” “having,” “includes” and “including,” are alsoopen-ended. For example, any method that “comprises,” “has” or“includes” one or more steps is not limited to possessing only those oneor more steps and also covers other unlisted steps.

The term “contaminate” or contaminated” includes where one substancecoats, is mixed with, or is dissolved in, in another substance.Contamination in any of these forms may be partial or complete.

The term “effective,” as that term is used in the specification and/orclaims, means adequate to accomplish a desired, expected, or intendedresult.

A “hydrophobic surface” refers to a surface with a water contact anglegreater than 90°, while a “hydrophilic surface” refers to a surface witha water contact angle smaller than 80°.

The term “oil” used herein encompasses crude oil, petroleum, as well asrefined or fractionated petroleum products and organic materials,including, fats, vegetable oils, fish oils, and animal oils.

“Remove” or “removing” includes effecting any measurable decrease in thesubstance being removed.

An “oleophobic surface” refers to a surface with an oil contact anglegreater than 90°, while an “oleophilic surface” refers to a surface withan oil contact angle smaller than 80°.

When used in the context of a chemical group, “hydrogen” means —H;“hydroxy” means —OH; “oxo” means ═O; “halo” means independently —F, —Cl,—Br or —I; “amino” means —NH₂ (see below for definitions of groupscontaining the term amino, e.g., alkylamino).

The term “saturated” as used herein means the compound or group somodified has no carbon-carbon double and no carbon-carbon triple bonds,except as noted below. The term does not preclude carbon-heteroatommultiple bonds, for example a carbon oxygen double bond or a carbonnitrogen double bond. Moreover, it does not preclude a carbon-carbondouble bond that may occur as part of keto-enol tautomerism orimine/enamine tautomerism.

The term “alkyl” refers to a monovalent saturated aliphatic group with acarbon atom as the point of attachment, a linear or branched, cyclo,cyclic or acyclic structure, and no atoms other than carbon andhydrogen. Thus, as used herein cycloalkyl is a subset of alkyl. Thegroups —CH₃ (Me), —CH₂CH₃ (Et), —CH₂CH₂CH₃ (n-Pr), —CH(CH₃)₂ (iso-Pr),—CH(CH₂)₂ (cyclopropyl), —CH₂CH₂CH₂CH₃ (n-Bu), —CH(CH₃)CH₂CH₃(sec-butyl), —CH₂CH(CH₃)₂ (iso-butyl), —C(CH₃)₃ (tert-butyl),—CH₂C(CH₃)₃ (neo-pentyl), cyclobutyl, cyclopentyl, cyclohexyl, andcyclohexylmethyl are non-limiting examples of alkyl groups. The term“haloalkyl” is a subset of substituted alkyl, in which one or morehydrogen has been substituted with a halo group and no other atoms asidefrom carbon, hydrogen and halogen are present. The groups, —CH₂F,—CH₂Cl, —CF₃, and —CH₂CF₃ are non-limiting examples of haloalkyl groups.

The term “nitrogen-containing heteroaryl” refers to a monovalentaromatic group with an aromatic carbon atom or nitrogen atom as thepoint of attachment, said carbon atom or nitrogen atom forming part ofan aromatic ring structure wherein at least one of the ring atoms isnitrogen, and wherein the group consists of no atoms other than carbon,hydrogen, aromatic nitrogen, aromatic oxygen and aromatic sulfur. Asused herein, the term does not preclude the presence of one or morealkyl group (carbon number limitation permitting) attached to thearomatic ring or any additional aromatic ring present. Non-limitingexamples of nitrogen-containing heteroaryl groups include imidazolyl,indolyl, indazolyl (Im), methylpyridyl, oxazolyl, pyridyl, pyrrolyl,pyrimidyl, pyrazinyl, quinolyl, quinazolyl, and quinoxalinyl.

The above definitions supersede any conflicting definition in any of thereferences that is incorporated by reference herein. The fact thatcertain terms are defined, however, should not be considered asindicative that any term that is undefined is indefinite. Rather, allterms used are believed to describe the invention in terms such that oneof ordinary skill can appreciate the scope and practice the presentinvention.

EXAMPLES

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

Example 1 Methods and Materials

Materials.

Poly(2-vinyl pyridine-b-dimethylsiloxane) block copolymer P5321(P2VP-b-PDMS 16,000-b-10,000 g/mol) was purchased from Polymer Source,Inc., Canada. 7 nm silica nanoparticles, 1,2-bis(triethoxysilyl)ethane,(3-bromopropyl)tri-methoxysilane, dichloromethane, 1,2-dichloroethaneand anhydrous toluene were all purchased from Sigma-Aldrich and used asreceived. Non-woven clothlike wipes made from cellulose andpolypropylene blends were used as received from workwipes. Waterpurified in a Milli-Q (Millipore) system was used during all theexperiments.

Characterization.

Air plasma treatment were carried out using PDC-002 plasma cleaner(Harrick Plasma company, US). Scanning electron microscopy (SEM) imageswere obtained on FEI Magellan scanning electron microscope. Contactangle measurements were performed with an Attension Theta system (KSVInstruments Ltd., Finland) at ambient temperature. Water droplets of 2μL were used for the water contact angles measurement in air. For theunderwater oil contact angles measurements, oil droplets(1,2-dichloroethane, ca. 2 μL) were dropped carefully onto the surfaceof the samples, which were fixed on the bottom of a glass containerfilled with water of different pHs. An average CA value was obtained bymeasuring the same sample at three different positions.

Example 2 Preparation of Poly(2-vinyl pyridine-b-dimethylsiloxane)Modified Material

The procedure for the preparation of the surface on the textile fabricwith switchable oleophilicity and oleophobicity in aqueous medium isschematically illustrated in FIG. 1. To introduce the nanostructures onthe surface of the textile fibers, silica nanoparticles were firstcoated on the textile fabric from a silica sol (20 mL 2% silicananoparticles (7 nm), 0.5 mL concentrated HCl and 0.5 mL1,2-bis(triethoxysilyl)ethane). Then the silica nanoparticles depositedon the textile fabric were functionalized with(3-bromopropyl)trimethoxysilane (BPS), which served as the anchoringlayer. Finally, the block copolymer of P2VP-b-PDMS was grafted onto thesurface through the quaternization reaction between the bromoalkylgroups and the pyridyl groups of the block copolymers. Scanningelectrical microscopy (SEM) measurements were carried out tocharacterize the surface morphologies of the textile surface before andafter the functionalization. As shown in FIGS. 2 a & b, the raw textilefabric typically consists of ribbon-like fibers with sizes of about 40μm in width and 5 μm in thickness and the fibers exhibit relativelysmooth surfaces. After the silica nanoparticle deposition and the blockcopolymer grafting, the textile fibers were not changed (FIG. 2 c),while clusters of several micrometers could be observed. Enlarged viewin FIG. 2 d reveals that the surface of the fibers was randomlydistributed with nanostructures and microscale clusters which arecomposed of aggregated nanostructures. These deposited nanostructuresand the clusters, along with the underneath inherent microscale fibers,constituted a hierarchically micro- and nanoscale surface roughness,which is believed to amplify the surface wetting properties.

Example 3 Properties of Poly(2-vinyl pyridine-b-dimethylsiloxane)Modified Substrate

The as-obtained block copolymer-grafted surface is of a relatively lowfree-energy and high roughness and its wettability is thereby evaluatedby contact angle measurements. For the as-prepared block copolymergrafted textile surface in air, the neutral (pH ˜6.5) water dropletformed a sphere with a contact angle of 157.2±4.2°, as shown in the leftpanel of FIG. 3 a, indicating a hydrophobic surface for neutral water.After 15 min of exposure to ambient air, the water droplet remained itsspherical form in spite of shrinkage due to the evaporation inducedtotal volume reduction indicating that the as-prepared surface is stableto neutral water. Moreover, as the raw untreated textile fabric exhibitsa hydrophilic surface property, the hydrophobicity of the as-preparedsurface demonstrates a successful grafting of the block copolymer, whichlowers the surface energy of the surface. The oil wettability of theas-prepared surface in air was also tested by using 1,2-dichloroethane(DCE) droplet as an indicator. As shown in FIG. 3 b, as soon as the oildroplet contacted the surface of the textile, it completely spread overthe surface within 50 ms, indicating the oleophilicity of theas-prepared surface.

P2VP, a weak polybase (pK_(a)˜4.7), exhibits pH-dependent wettability,being hydrophobic at high pHs but hydrophilic at low pHs, owing toprotonation and deprotonation processes of pyridyl groups. As shown inFIG. 4 a, when an acidic water droplet (pH 1.0) was applied on theP2VP-b-PDMS grafted textile fabric surface in air, it gradually spreadout completely within about 10 seconds and wetted the textile,indicating the hydrophilicity of the surface to acidic water. Theacid-exposed surface can recover its hydrophobicity easily by rinsingwith neutral water and then drying with N₂ flow and this process can bequickly finished at room temperature within 2 minutes and does notinvolve the use of extreme heating temperature or solvent treatment.This is mainly because that the PDMS segment in the block copolymer hasa low glass transition temperature (Tg, ca. −62° C. according to thesupplier) and thus it owns a high flexibility and thus can be consideredas a liquid polymer at ambient temperature. Therefore, and without beingbound by theory, it is expected that, upon drying, the PDMS segments,which are more hydrophobic than the P2VP segments, spontaneously stretchand move to the exterior of the grafted block copolymer, which recoversthe hydrophobicity of the prepared surface. FIGS. 4 b & c presentwetting behaviors of water droplets with different pHs on the blockcopolymer grafted textile. It is observed that the block copolymergrafted textile could be fully wetted by water with pH=2.0 within 160seconds, but is stably hydrophobic to water of pH≧3.0. Clearly, thewater droplet with pH 1 wets the prepared surface much faster than thatwith pH 2. A clear-cut, abrupt switch of surface water wettabilitywithin a small pH range makes this material desirable for manyapplications.

These results confirm that P2VP-b-PDMS grafted textile exhibits tunablewetting behavior to water, depending on water pH, switching betweenhydrophobicity and hydrophilicity. The switchable water wettability ofthe surface is expected to affect its oil wettability in aqueous media.FIG. 5 presents the oil wettability of the P2VP-b-PDMS grafted textileunder water of different pH values, with DCE representing an oil phase.As shown in FIG. 5 a, as soon as the DCE droplet touched the surface ofthe block copolymer grafted textile, which was immersed in water of pH6.5, it immediately diffused into the textile within 0.12 s, indicatinga oleophilic property of the surface in pH neutral aqueous medium. FIG.5 b shows an underwater oil uptake process by the block copolymergrafted textile. The oil red stained DCE droplets were dropped at thebottom of the beaker containing water of pH 6.5, and then a piece of theblock copolymer grafted textile was lowered down to approach the DCEdroplets. On contact, the textile immediately sucked up the DCE dropletswithout leaving behind any residues. This simple experiment reveals thatthe block copolymer grafted materials are promising sorbents forremoving oil from water.

As discussed above, the surface prepared by the method described aboveis hydrophobic to water at pH≧3, which means the surface is nonwettablein these aqueous media. As a result, when the block copolymer graftedtextile is immersed in neutral water, the surface is still covered withthe oleophilic PDMS chains, and therefore once an oil droplet contactsthe surface, oil wets the surface preferentially over water owing to theoleophilic surface property (FIG. 5 c). Additionally, it was found thatthe surface was still oleophilic even after 24 h of immersion in waterof pH 6.5, which demonstrates that the oleophilic property of theprepared surface is relatively stable under pH neutral aqueous media.

On the other hand, it has been reported that air can be trapped insidethe rough grooves of the hydrophobic surface under water. Theas-prepared block copolymer grafted textile surface is hydrophobic inair. In some embodiments, air will be trapped inside the grooves whenthe rough surface is immersed in water. A complex interfacial system,i.e., a four phase system (air-solid-oil-water), will then be formedwhen an oil droplet contacts such a surface.

In contrast to neutral water, when the textile was immersed in acidicwater with pH of 2.0, the oil wettability of the surface reversedcompletely. As shown in FIG. 5 d, the DCE contact angle was 165.3° inthe acidic water, indicating the oleophobicity of the block copolymergrafted textile in acidic water. FIG. 5 d shows a photograph of DCEdroplets sitting on the surface of the textile under acidic water, andclearly the textile was non-wettable to oil. As has been discussedabove, the block copolymer grafted surface can be turned intohydrophilic due to the protonation of pyridyl groups in acidic water,and thus when immersed in acidic water, water can easily wet the surfaceand diffuse into micro- and nanostructures of the textile, forming awater trapped composite interface. In some embodiments, this newcomposite interface contributes to the oleophobic property of thesurface under water (FIG. 5 f).

After being rinsed with neutral water and dried with N₂ flow, theacid-wetted surface can easily recover its hydrophobic and oleophilicproperties in neutral aqueous medium, thus suggesting its switchableoleophobicity and oleophilicity in aqueous media. It turns out that thereversible cycle of the surface wettability (both in air and aqueousmedia) can be repeated for many times without any change in thepH-responsive property of the surface (FIG. 6).

To better understand the switching of the oil wettability on the blockcopolymer grafted surface in different aqueous media, equation (1)derived from Young's equation can be employed to depict the contactangle of an oil on flat surface in the existence of water bulk phase:

$\begin{matrix}{{\cos \; \theta_{ow}} = \frac{{\gamma_{oa}\cos \; \theta_{oa}} - {y_{wa}\cos \; \theta_{wa}}}{\gamma_{ow}}} & (1)\end{matrix}$

where γ_(oa), γ_(wa), and γ_(ow) are surface tensions of the oil/air,water/air, and oil/water interfaces, respectively. θ_(ow), θ_(oa), andθ_(wa) are the contact angle of oil in water, oil in air, and water inair, respectively. According to this equation, it can be seen that thecontact angle of oil in water can be adjusted by tuning the θ_(oa), andθ_(wa). Taking DCE as an example, its interfacial tension with air(γ_(oa)) is 24.15 mNm⁻¹, and the water surface tension (γ_(wa)) is 73.0mNm⁻¹. The DCE/water interfacial tension (γ_(ow)) is 28.1 mNm⁻¹. In airthe DCE contact angle on the block copolymer grafted smooth surface(θ_(oa)) was 13.5°. However, for water with different pH values, thecontact angle in air can be changed from 91.2° (pH 6.5) to 52.1° (pH2.0), due to the pH-tunable wettability of P2VP chains. As a result fromequation (1), the oil contact angle in these aqueous media are 27° (pH6.5) and 139.5° (pH 2.0), indicating the switching of the wettabilityfrom oleophilicity to oleophobicity. The calculated results areconsistent with the experimental results where the flat surface (i.e.,silicon wafer) with the grafted block copolymer showed oil contactangles of ca. 36° in water of pH 6.5 and 138° in water of pH 2.0,respectively. As for the grafted block copolymer grafted textiles, theirhierarchical micro- and nanostructures further amplified their oilwettability making them oleophilic and oleophobic surfaces in differentaqueous media.

From the above results, the P2VP-b-PDMS grafted textiles exhibitswitchable oleophobicity and oleophilicity in aqueous medium withdifferent pH values. Such a smart surface is expected to be very usefulto materials for underwater applications.

Example 4 Underwater Application of Poly(2-vinylpyridine-b-dimethylsiloxane) Modified Substrate

As an example of an application, it was shown that these P2VP-b-PDMSgrafted textiles can be used for the controllable water/oil separation.The P2VP-b-PDMS grafted textiles were fixed between two glass tubes as aseparation membrane. The simple oil/water separation setup is shown inFIG. 7. A mixture of commercial gasoline and pH neutral water was pouredinto the upper glass tube, and, due to the oleophilicity andhydrophobicity of the textile surface, only gasoline quickly passedthrough the textile and water could not and thus was retained on top ofthe textile in the upper glass tube (FIG. 7 a). However, when thetextile was first simply wetted by an acidic water (pH<2) (withoutdrying) and then used under otherwise same conditions, an inversedwater/oil separation process was realized. As shown in FIG. 7 b, in thiscase, water, which is neutral pH, in the mixture selectively passedthrough the textile quickly, leaving behind the gasoline retained in theupper tube. The ease with which the permeability of the block copolymergrafted textile toward oil and water is selectively switched means thesame piece of material can be used for different separation purposes.

Example 5 Polyurethane-based Poly(2-vinyl pyridine-b-dimethylsiloxane)Modified Substrate

A three-dimensional porous polyurethane foam was employed as a substratefor the P2VP-b-PDMS grafting according to the same procedure as detailedin Example 2 above. The modified foams exhibit oleophilicity in neutralaqueous medium, and can be easily switched into oleophobic when wettedby acidic water. FIGS. 8 a & b shows the oil capture and release processby the functionalized foam. DCE of about 2 mL stained with oil red dyewas dropped into neutral water, and a functionalized foam was held toapproach the DCE phase in water, and upon contact, the DCE was quicklysucked up by the foam without any residues left behind (FIG. 8 a & b).Moreover, the absorbed oil can be easily released from the foam when theoil-loaded foam was transferred into an acidic water (pH 2.0) withgentle shaking and squeezing (FIG. 8 c), which is caused by theswitching of the surface wettability from oleophobicity tooleophilicity. After washing with neutral water and drying, the foam canrecover its oleophilic property and can be used for oil removal again.Thus, the material is recyclable, reducing oil cleanup costsignificantly.

Example 6 Core-Shell Nanostructure-based Poly(2-vinylpyridine-b-dimethylsiloxane) Modified Substrate

Core-shell nanostructures, with Fe₃O₄ magnetic nanoparticles being thecore and mesoporous silica being the shell, were employed as substrateand were modified with P2VP-b-PDMS to prepare responsive functionalizednanoparticles (FIGS. 9 a and 9 b). The liquid marbles were prepared byencapsulating water droplets with the responsive functionalizednanoparticles (FIG. 9 c). The such-prepared liquid marbles have apH-responsive rupture behavior (FIG. 9 c). The mesoporous shell of thefunctionalized nanoparticles were further loaded with photo-acidgenerator (PAG) (FIG. 9 d). The liquid marble prepared using thePAG-loaded functionalized nanoparticles rupture under UV illumination(FIG. 9 d), avoiding the requirement of adjusting the bulk pH of thesystem. Due to the magnetic core materials of the functionalizednanoparticles, the thus-prepared liquid marbles can be remotelymanipulated by an external magnetic field (FIG. 9 c). We envision thatthe potential applications of such remotely controllable liquid marblesbased on the surface-modified nanostructures will include smart deliveryof water-soluble agents to initiate chemical reactions on demand,channel-free microfluidic systems, and sensors with visual indicationcapability.

All of the materials and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the materials and methods of this invention have beendescribed in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to materialsand to the methods and in the steps or in the sequence of steps of themethod described herein without departing from the concept, spirit andscope of the invention. More specifically, it will be apparent thatcertain agents which are both chemically and/or structurally related maybe substituted for the agents described herein while the same or similarresults would be achieved. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

1. A surface-modified material comprising a substrate covalently bondedto a polymer, wherein the surface of the surface-modified material isoleophilic and/or hydrophobic at a first condition and oleophobic and/orhydrophilic at a second condition, and wherein the polymer comprises awettability-responsive polymer, polymer segment or polymer blockcomprising poly(N-isopropylacrylamide), polyacrylamide, polypyrrole,polythiophene, polyaniline, poly(2-vinylpyridine),poly(4-vinylpyridine), poly(acrylic acid), poly(methylacrylic acid),poly(2-(diethylamino)ethylmethacrylate, poly(spiropyran methacrylate),poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, or poly[2-(methacryloyloxy)-ethyl-trimethylammoniumchloride].
 2. The surface-modified material of claim 1, wherein thesurface-modified material is oleophilic in aqueous media at a firstcondition and oleophobic in aqueous media at a second condition.
 3. Thesurface-modified material of claim 1, wherein the surface-modifiedmaterial is oleophilic in air at a first condition and oleophobic in airat a second condition.
 4. The surface-modified material of claim 1,wherein the substrate comprises a plurality of imbedded nanostructures.5. The surface-modified material of claim 1, wherein the first andsecond conditions are selected from the group consisting of a certaintemperature, voltage, pH, illuminance, pressure, and a combinationthereof.
 6. The surface-modified material of claim 1, wherein the secondcondition is the changed status of the first condition.
 7. Thesurface-modified material of claim 4, wherein the nanostructurescomprise nanoparticles, nanowires, nanorods, nanobelts, nanotubes,layered nanostructures, or a combination thereof.
 8. Thesurface-modified material of claim 4, wherein the nanostructurescomprise silica, carbon, metal, metal oxide of the metal, hybrid of themetals, hybrid of the metal oxides, or polymers.
 9. The surface-modifiedmaterial of claim 8, wherein the nanostructures comprise silica.
 10. Thesurface-modified material of claim 4, wherein the nanostructures have anaverage size from around 1 nm to 10 μm in at least one dimension. 11.The surface-modified material of claim 1, wherein the substrate does notcomprise a plurality of imbedded nanostructures.
 12. Thesurface-modified material of claim 1, wherein the polymer comprises ablock copolymer or mixed polymer.
 13. The surface-modified material ofclaim 12, wherein the polymer comprises a block copolymer comprising twoor three blocks.
 14. The surface-modified material of claim 13, whereinthe block copolymer comprises at least one wettability-responsive block.15. The surface-modified material of claim 14, wherein thewettability-responsive block is poly(N-isopropylacrylamide),polyacrylamide, polypyrrole, polythiophene, polyaniline,poly(2-vinylpyridine), poly(4-vinylpyridine), poly(acrylic acid),poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, or poly[2-(methacryloyloxy)-ethyl-trimethylammoniumchloride].
 16. The surface-modified material of claim 13, wherein theblock copolymer comprises at least one hydrophobic block.
 17. Thesurface-modified material of claim 16, wherein the hydrophobic block ispoly(acrylonitrile), poly(phenyl methyl siloxane), polystyrene,poly(4-dimethylsilyl styrene), poly(4-methyl styrene), poly(dimethylsiloxane), polyethylene, polypropylene, poly(isobutylene), polyamide, orpoly(vinylidene fluoride).
 18. The surface-modified material of claim11, wherein the polymer comprises a mixed polymer comprising at leastone hydrophobic homogenous polymer and one polymer that is responsive towettability.
 19. The surface-modified material of claim 18, wherein thehydrophobic homogenous polymer is poly(acrylonitrile), poly(phenylmethyl siloxane), polystyrene, poly(4-dimethylsilyl styrene),poly(4-methyl styrene), poly(dimethyl siloxane), polyethylene,polypropylene, poly(isobutylene), polyamide, or poly(vinylidenefluoride).
 20. The surface-modified material of claim 18, wherein thewettability-responsive polymer is poly(N-isopropylacrylamide),polyacrylamide, polypyrrole, polythiophene, polyaniline,poly(2-vinylpyridine), poly(4-vinylpyridine), poly(acrylic acid),poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],or mixtures thereof.
 21. The surface-modified material of claim 1,wherein the substrate comprises a textile, a membrane, a polymer foam, ametal mesh, a metal foam, paper, glass, or nanostructures.
 22. Thesurface-modified material of claim 21, wherein the textile, membrane,paper, metal mesh, metal foam or polymer foam has an average pore sizein the range from 10 nm to 5,000 μm.
 23. The surface-modified materialof claim 1, wherein the substrate comprises a nonporous solid.
 24. Thesurface-modified material of claim 21, wherein the textile, membrane, orpolymer foam comprises cellulose, nylon, polyester, polyethyleneterephthalate, polyurethane polylactide, polypropylene, polyethylene,polysulfone, polyamide, polyvinyl chloride, polytetrafluoroethylene,polycarbonate, polyacrylonitrile, polybutylene terephthalate, polyimide,polymethyl methacrylate, polyetheretherketone, polyetherketone,polyetherimide, polyethersulfone, polymethylpentene, polyoxymethylene,polyphthalamide, polyphenylene oxide, polyphenylene sulfide, ethylenepropylene rubber, styrene butadiene rubber, ethylene propylene dienemonomer rubber, chitosan, alginate, gelatin,poly(N-isopropylacrylamide), poly(4-vinylpyridine),poly(2-vinylpyridine), polydimethylsiloxane, poly(phenyl methylsiloxane), poly(4-dimethylsilyl styrene), poly(4-methyl styrene),poly(isobutylene), poly(N-isopropylacrylamide), polyacrylamide,polypyrrole, polythiophene, polyaniline, poly(acrylic acid),poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl (3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],polyvinylpyrrolidone, or mixtures or blends thereof.
 25. Thesurface-modified material of claim 21, wherein the metal mesh or metalfoam comprises metal, metal oxide of the metal, metal chloride of themetal, metal hydroxide of the metal, alloy of the metals, hybrids of themetal oxides, hybrids of the metal chlorides, or hybrids of the metalhydroxides.
 26. The surface-modified material of claim 25, wherein themetal comprises at least one of copper, iron, nickel, titanium, zinc,aluminum, silver, gold, palladium, platinum, silicon, vanadium,zirconium, cobalt, lead, chromium, barium, manganese, magnesium,yttrium, hafnium, thallium, indium, tin, arsenic, selenium, tellurium,bismuth, gallium, germanium, cadmium, iridium, tungsten, tantalum,niobium, molybdenum, strontium, calcium, an alloy thereof, an oxidethereof, or a mixture thereof.
 27. The surface-modified material ofclaim 21, wherein the nonporous solid comprises the same chemicalcompositions as the textile, filter membrane, or polymer foam in claim22.
 28. The surface-modified material of claim 23, wherein the nonporoussolid comprises the same chemical compositions as the metal mesh ormetal foam in claim
 23. 29. The surface-modified material of claim 1,wherein the polymer was bonded to the substrate through a grafting toand/or grafting from process.
 30. The surface-modified material of claim29, wherein the grafting from process comprises atom transfer radicalpolymerization or reversible addition-fragmentation chain transferpolymerization.
 31. The surface-modified material of claim 29, whereinthe grafting to process comprises functionalized polymer moleculesreacting with complementary functional groups located on the substratesurface to form tethered chains.
 32. The surface-modified material ofclaim 31, wherein the functional groups of the functionalized polymermolecules comprise amino groups, pyridyl groups, carboxy groups, and/orhydroxy groups.
 33. The surface-modified material of claim 31, whereinthe complementary functional groups located on the substrate surfacecomprise epoxy groups, amino groups, carboxy groups, hydroxy groups,and/or haloalkyl groups.
 34. The surface-modified material of claim 31,wherein the complementary functional groups are introduced on thesubstrate surface by a silanization reaction between a silane and thesubstrate.
 35. The surface-modified material of claim 34, wherein thesilane comprises an epoxy group, amino group, carboxy group, hydroxylgroup, and/or haloalkyl group.
 36. A surface-modified materialcomprising a substrate covalently bonded to a polymer, wherein thesubstrate comprises a plurality of silanized silica particles and thepolymer comprises a plurality of pyridyl groups.
 37. Thesurface-modified material of claim 36, wherein the substrate furthercomprises a textile, a metal mesh, paper, a metal foam or a polymerfoam.
 38. The surface-modified material of claim 37, wherein thesubstrate is a textile.
 39. The surface-modified material of claim 38,wherein the textile comprises cellulose.
 40. The surface-modifiedmaterial of claim 38, wherein the textile comprises polypropylene. 41.The surface-modified material of claim 37, wherein the substratecomprises a polymer foam.
 42. The surface-modified material of claim 41,wherein the polymer foam is a polyurethane.
 43. The surface-modifiedmaterial of claim 36, wherein the silanized silica particles are furtherdefined as silanized silica nanoparticles.
 44. The surface-modifiedmaterial of claim 36, wherein the silanized silica particles weresilanized using (3-bromopropyl)trimethoxysilane.
 45. Thesurface-modified material of claim 36, wherein the polymer is apoly(2-vinyl pyridine-b-dimethylsiloxane) block copolymer.
 46. A methodof separating oil from water, comprising: obtaining a surface-modifiedmaterial according to claim 36; contacting the surface-modified materialwith a mixture comprising oil and water; and adjusting the pH of themixture until more oil than water adheres to the surface-modifiedmaterial.
 47. A surface-modified material comprising a substratecovalently bonded to a polymer, wherein the polymer comprises aplurality of nitrogen-containing heteroaryl_((C3-12)) groups, andwherein the surface of the surface-modified material is oleophilic at afirst condition and oleophobic at a second condition.
 48. Thesurface-modified material of claim 47, wherein the nitrogen-containingheteroaryl_((C3-12)) groups are further defined as pyridyl groups. 49.The surface-modified material of claim 47, wherein the substratecomprises a plurality of imbedded nanostructures. 50-78. (canceled) 79.The surface-modified material of claim 47, wherein the first and secondconditions are selected from the group consisting of a certaintemperature, voltage, pH, illuminance, pressure, and a combinationthereof.
 80. (canceled)
 81. The surface-modified material of claim 21,wherein the nanostructures have an average size between 1 nm and 100 μmin at least one dimension.
 82. (canceled)
 83. The surface-modifiedmaterial of claim 21, wherein the nanostructures are porous.
 84. Thesurface-modified material of claim 83, wherein the pore size of theporous nanostructures is between 0.1 nm to 200 nm.
 85. Thesurface-modified material of claim 21, wherein the nanostructurescomprise core-shell nanostructures.
 86. The surface-modified material ofclaim 85, wherein the core-shell structures comprise a magnetic core anda shell.
 87. The surface-modified material of claim 85, wherein thecore-shell structures comprise a hollow core and a shell.
 88. Thesurface-modified material of claim 86, wherein the shell is porous. 89.The surface-modified material of claim 88, wherein the pore size of theporous shell is porous between 0.3 nm to 200 nm.
 90. Thesurface-modified material of claim 86, wherein the shell is nonporous.91. The surface-modified material of claim 85, wherein the core of thecore-shell nanostructures comprises the same chemical compositions asthe nanostructures in claim
 82. 92. The surface-modified material ofclaim 85, wherein the shell of the core-shell nanostructures comprisesthe same chemical compositions as the nanostructures in claim
 82. 93.(canceled)
 94. (canceled)
 95. The surface-modified material of claim 8,wherein the polymers comprise cellulose, nylon, polyester, polyethyleneterephthalate, polyurethane polylactide, polypropylene, polyethylene,polysulfone, polyamide, polyvinyl chloride, polytetrafluoroethylene,polycarbonate, polyacrylonitrile, polybutylene terephthalate, polyimide,polymethyl methacrylate, polyetheretherketone, polyetherketone,polyetherimide, polyethersulfone, polymethylpentene, polyoxymethylene,polyphthalamide, polyphenylene oxide, polyphenylene sulfide, ethylenepropylene rubber, styrene butadiene rubber, ethylene propylene dienemonomer rubber, chitosan, alginate, gelatin,poly(N-isopropylacrylamide), poly(4-vinylpyridine),poly(2-vinylpyridine), polydimethylsiloxane, poly(phenyl methylsiloxane), poly(4-dimethylsilyl styrene), poly(2-methyl styrene),poly(isobutylene), poly(N-isopropylacrylamide), polyacrylamide,polypyrrole, polythiophene, polyaniline, poly(acrylic acid),poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],polyvinylpyrrolidone, or mixtures or blends thereof.
 96. Thesurface-modified material of claim 82, wherein the polymers comprisecellulose, nylon, polyester, polyethylene terephthalate, polyurethanepolylactide, polypropylene, polyethylene, polysulfone, polyamide,polyvinyl chloride, polytetrafluoroethylene, polycarbonate,polyacrylonitrile, polybutylene terephthalate, polyimide, polymethylmethacrylate, polyetheretherketone, polyetherketone, polyetherimide,polyethersulfone, polymethylpentene, polyoxymethylene, polyphthalamide,polyphenylene oxide, polyphenylene sulfide, ethylene propylene rubber,styrene butadiene rubber, ethylene propylene diene monomer rubber,chitosan, alginate, gelatin, poly(N-isopropylacrylamide),poly(4-vinylpyridine), poly(4-vinylpyridine), polydimethylsiloxane,poly(phenyl methyl siloxane), poly(4-dimethylsilyl styrene),poly(4-methyl styrene), poly(isobutylene), poly(N-isopropylacrylamide),polyacrylamide, polypyrrole, polythiophene, polyaniline, poly(acrylicacid), poly(methylacrylic acid), poly(2-(diethylamino)ethylmethacrylate,poly(spiropyran methacrylate), poly(methacryloyl ethylene phosphate),poly[2-(methacryloyloxy)ethyl]-dimethyl(3-sulfopropyl)ammoniumhydroxide, poly[2-(methacryloyloxy)-ethyl-trimethylammonium chloride],polyvinylpyrrolidone, or mixtures or blends thereof.
 97. (canceled) 98.(canceled)
 99. The surface-modified material of claim 7, wherein thecore-shell nanostructures comprise the same composition as in claim thecore-shell nanostructures in claim
 85. 100. The surface-modifiedmaterial of claim 97, wherein the porous nanostructures are loaded withlight-sensitive substances in their pore space.
 101. Thesurface-modified material of claim 99, wherein the core-shellnanostructures are loaded with light-sensitive substances in their shelland/or core space.
 102. The surface-modified material of claim 83,wherein the porous nanostructures are loaded with light-sensitivesubstances in their pore space.
 103. The surface-modified material ofclaim 85, wherein the core-shell nanostructures are loaded withlight-sensitive substances in their shell and/or core space.
 104. Thesurface-modified material of claim 100, wherein the light-sensitivesubstances comprise photoacid generators, photoinitiators, photobasegenerators, photocatalysts, or mixtures or blends thereof.
 105. Thesurface-modified material of claim 104, wherein the photoacid generatorcomprises bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate,bis(4-tert-butylphenyl)iodonium p-toluenesulfonate,bis(4-tert-butylphenyl)iodonium triflate,boc-methoxyphenyldiphenylsulfonium triflate,(4-bromophenyl)diphenylsulfonium triflate,(tert-butoxycarbonylmethoxynaphthyl)-diphenylsulfonium triflate,(4-tert-butylphenyl)diphenylsulfonium triflate, diphenyliodonium9,10-dimethoxyanthracene-2-sulfonate, diphenyliodoniumhexafluorophosphate, diphenyliodonium nitrate, diphenyliodoniumperfluoro-1-butanesulfonate, diphenyliodonium p-toluenesulfonate,diphenyliodonium triflate, (4-Fluorophenyl)diphenylsulfonium triflate,N-hydroxynaphthalimide triflate,N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butane sulfonate,(4-iodophenyl)diphenylsulfonium triflate,(4-methoxyphenyl)diphenylsulfonium triflate,2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,(4-methylphenyl)diphenylsulfonium triflate, (4-methylthiophenyl)methylphenyl sulfonium triflate, (4-phenoxyphenyl)diphenylsulfonium triflate,(4-phenylthiophenyl)diphenylsulfonium triflate, triphenylsulfoniumtriflate, or mixtures or blends thereof.
 106. The surface-modifiedmaterial of claim 104, wherein the photoinitiator comprisesazobisisobutyronitrile, benzoyl peroxide, or mixtures or blends thereof.107. The surface-modified material of claim 104, wherein the photobasegenerator comprises malachite green carbinol base.
 108. Thesurface-modified material of claim 104, wherein the photocatalystcomprises TiO₂, ZnO, SnO₂, ZrO₂, CdS, ZnS, WO₃, SiC, Si, InP, GaP, CuO,Cu₂O, CdTe, CdSe, Fe₂O₃, In₂O₃, In₂S₃, CuS, PbS, PbO, Si₃N₄, GaAs, GaN,AlGaInP, SiGe, or AlGaAs.